There are many places to purchase T5 adaptors from, below i will list some different resources for buying them.
Most T5 adaptors are rated to last for 10 years, and can cost anywhere from $10-$30. Most are manufactured in China, and can be found in many retail shops and electrical retailers.
T5 adaptors - The green guys, can install hardware and provide government funding in NSW, Australia - for small and medium businesses to upgrade lights to energy efficiency T5 adaptors and lights.
Energy efficiency - More info about what the green guys can do for your business